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Re: Serial date, Excel, Lotus, MJD, PolyForth

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"Ed" <invalid@nospam.com> wrote in message
news:kmf28f$n8d$1@speranza.aioe.org...

> Here's a question for the computer historians.
>
> Who invented - or was the first to use - the serial date system
based
> on year 1900 ?
>
> What's good about year 1900?  Well it means that for the epoch
we're
> most interested in, serial dates can be stored as a single
16-bit number
> and the computer math required to manipulate them is easy.
>
> Googling one finds this serial calendar referred to as the
> "Excel Serial Day Number"
> http://www.fourmilab.ch/documents/calendar/
>
> Another Bill Gates' innovation?  Alas no.  Microsoft admits they
> took it from Lotus 123 - a leading spreadsheet program of the
day.
> Oh, and yes, there was a bug in the Lotus implementation which
has
> faithfully been copied to this day - namely, the assumption that
1900
> was a leap year!
>
> So what's this got to do with Forth?  As it happens Forth Inc
also had
> a serial calendar based on year 1900 which they called MJD or
> "Modified Julian Day".  Google "MJD" however, and one will find
> it refers to an entirely different serial date system which
predated
> Forth Inc.  So how was it that Forth Inc came to call their
system
> "MJD" ?  Were they unaware the name and acronym had already been
> taken?
>
> Back to the question I posed at the beginning.  Who invented -
or was
> the first to implement - the 1900 serial date system?  Google it
and
> the earliest reference one will find is Lotus 123.  But Lotus
was
> released in 1983 and Forth Inc predated it.  So how did Forth
Inc come
> its serial calendar and when?
>
> A final twist.  The programmer who wrote the first version of
Lotus 123
> was one Jonathan Sachs - the same Jonathan Sachs who implemented
> STOIC, a variant of Forth, in the mid 1970's.
>
>

Your initial question wasn't restricted to computing platforms.
In which case, your answer is likely here:

http://en.wikipedia.org/wiki/Newcomb's_Tables_of_the_Sun
http://en.wikipedia.org/wiki/January_0
http://en.wikipedia.org/wiki/Epoch_(reference_date)#Computing


RP

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Serial date, Excel, Lotus, MJD, PolyForth "Ed" <invalid@nospam.com> - 2013-05-09 12:40 +1000
  Re: Serial date, Excel, Lotus, MJD, PolyForth "Elizabeth D. Rather" <erather@forth.com> - 2013-05-08 20:04 -1000
    Re: Serial date, Excel, Lotus, MJD, PolyForth Mark Wills <forthfreak@gmail.com> - 2013-05-09 00:17 -0700
    Re: Serial date, Excel, Lotus, MJD, PolyForth "Elizabeth D. Rather" <erather@forth.com> - 2013-05-08 22:18 -1000
      Re: Serial date, Excel, Lotus, MJD, PolyForth "Ed" <invalid@nospam.com> - 2013-05-10 12:19 +1000
    Re: Serial date, Excel, Lotus, MJD, PolyForth Alex McDonald <blog@rivadpm.com> - 2013-05-09 06:37 -0700
    Re: Serial date, Excel, Lotus, MJD, PolyForth C G Montgomery <cgm@physics.utoledo.edu> - 2013-05-09 17:30 -0400
    Re: Serial date, Excel, Lotus, MJD, PolyForth "Ed" <invalid@nospam.com> - 2013-05-11 14:57 +1000
  Re: Serial date, Excel, Lotus, MJD, PolyForth "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-05-09 18:41 -0400

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